Program-selecting circuits



Why 24, 1927. 1,629,552

M. ECSTRIEBY PROGRAM SELECTING CIRCUITS Filed D80. 10. .1923

A lnoudlre [Iii- 51:

Jfriez I W J ATTORNEY F. 3 y INVENTOR Patented May 24, 1927.

UNITED STATES PATENT OFFICE.

MAURICE E. STRIEBY, 0F MILLBURN, NEW JERSEY, ASSIGNOR '10 AMERICANTEl'iE PHONE AND TELEGRAPH'GOMPANY, .A. CORPORATION OF NEW YORK.

PROGRAM-SELECTING cmcurrs.

Application filed December 10, 1923. Serial No.6?9, 721.

This invention relates to transmission systems for transmitting programsover wires, and more particularly to arrangements for the selection ofprograms for such systems.

lVhere wire lines, such as ordinary telephone lines, for example, areused for the transmission of programs, such as news, leotures, concerts,and the like. it is desirable that some arrangement be provided wherebythe subscriber, may auton'iatically select the particular program whichhe desires to hear. In accordance with the presentinvention, itisproposed to accomplish this result by providing a selective switch atthe central oflice which may be clirectively controlled by thesubscriber to connect the. terminals of the subscribers line to theterminals of any one of a. number of trunks each leading to a dif-'ferent program. i By the use of a directively controlled selective.switch for selecting a program, it becomes immaterial whether theprogram be transmitted at "oice frequencies or carrier frequencies, andit also becomes immaterial -whether the several programs be transmittedat thesame frequency or whether different carrier frequencies are usedfor differentprograms The directive switch may becontrolled by impulsesor groups of impulses of alternating current and the source of currentfor operating the switches may be located either at the central'stationor at the subscribers station Preferabl the switches are operated inaccordance with the present invention over the sides of the line inseries.

The inven'tion'will now be more fully understood when read in connectionwith the accompanying drawing, Figure l of which illustrates .how adirectii e switch operated by alternating. current may be used to-selectprograms transmitted at ordinary telephonic t're uencies; Fig. 2 ofwhich shows how a simi ar switch may be used to select carrier Frequencyprograms, and Fig. 3 of which shows a. circuit arrangement similartothat of Fig. 2 but so arranged thatthe alternatingcurrent source foroperating the switches willbe located at the central station. i v

Referring to'Fig; 1,- L designates, an ordinary telephone transmissionline terminating in the; usual subscribers set S at, one endandterminating at the central oflice in the SM, a switchin usualswitching jackJ. Normally the tele phone line L is connected over thecontacts of a cutoff relay GO to the windings of the line relay LR. Theline relay, as is usual, may comprise two windings, each of about 1000ohms. The upper winding is associated with the tip side of the'line andis inductive. The lower winding is associated with the ring side'of theline but is non-inductive and consequently, does not-m netize the core01' the relay when current ows through said winding. The cut-01f relayCO is so arranged that when it is operated the line relay LR isdisconnected from the line; L and the line is connected directly to thetip and ring terminals of thejack J.

In order that the line may be used for program transmissionpurposes'dnrin such time as it is not being used for or inar telephonepurposes, a program receiver such asthe loud speaker-LS 1s providedat-the subscriber statiom'said receivingdevice being bridged across theline through the back contact of the switchhoo'k 10. hen the substationset S is used for ordinary telephonic purposes, the removal of thereceiver from the switchho'ok opens the circuit of the loud speaker LSso that it may not be thenused for receiving programs. At the centralofiicesa. pair of conductors 11 are con nected. from the back contactsof the cutoff relay O0 to the wipers 12 of a directive switch DR. Theswitch DR may he stepped by means of the stepping magnetSM intoconnection with any one of a number of trunks A, B, C or D, leading todifierent voice frequency programs.

In order to operate the stepping ma net I device such as a dia or key Kis provided at the subscribers station for sending impulses ofalternating current-over the line to energize the 'marginal steppingrelaySR. The source of a1- 'ternating current at the subscribers stationis bridged across the line over the back contact ot the switchhook 10.The alt-ernat- 'ing curreutior operating the switches may be obtainedfrom the power mains at the subscribers premises. The alternating cur-'1'-ent relay'SR is connected across the back contacts of the cut-offrelay CO in parallel with the windings of the line relay LR.-

The operation is as follows: When the line L isnot in use for telephonepurposes and the subscriber desires to hear a program, such as C, forexample, the subscril-ier Wlll merely actuate the dial or key K to sendimpu ses from the source G through the :tuned bridge (xmtrolled by thekey K. These impulsesspuss from one terminal of the transformer 13, overthe key K, buck contactvof the switchhook-IO, over the ring side of theline L, lower back Contact of the cut-off relay GO, through the tunedcircuit of the. alternating current relay SR, Over the upper backcontact of the cut-off relay-CO, over the tip side of the line L to theopposite terminal of the transformer .13. The ringer at. the subscribersstation is ordinarily tuned to vrespond to n fre- 'queucy of about '20cycles per second, and since the frequency of the alternating currentsupplied 'to the ower mains at the subscribers' stat-ionnwil. usually bein the neighborhood v0.1? (50 cycles, it will hc .apparout that thecurrent impressed upon the line by the 'key'K will not '-.operu.tethe'subscribers bell. The line relay LR is not responsive tolternatingcurrent; The current flowing through the relay SR energizessnid relay so 'that thefimpulses sentby the key K areftrnnsmitted by therelayv SR to the stepping magnet SM, Accordingly, the dl.

i l-ECtlVQ [switch DR is operuted step by step 'by themechanismconventionally indicated to adviz'nce the wipers12totheter1nina1s of [th trunk leading to the program C, The currentsfor this program are now transmitted overthe wip'erslil and conductors11,

7 .over the back contacts of the cut-oil relay ,CO and over the line Lto the loudspeaker -IlSr i If, while the circuit is being; used for.pro'- gram purposes, the subscriber desires to make {1itelephone,call,,he merely removes the receiver from. the jsw-itchhook in theusual manner, The 10nd speaker-LS is disconnected-acute back Contact ofthe im}:-

. t t e lished through the substation set from bat- =tery ,'through theupper winding of tho-line relhyg-LB, over thevbnckfcontnct of the cut,

off relay CQ, over the tip "side-of the line .1), over the switchhookl0,.bi1;.ck over,the

ring side ofthe line L, back contact of the cnt-ofi' relay CO andthrough the noninductive winding of the relayL'R .to ground. The linerelay LR is et once energlzedand upon attracting its armature, causesthe hue lam (not shown). to;glow in the man man ner. The-operator, uponnoticing this sigmil, will insert the plugofthe cord circnlt into thejack J, thereby'nctneting the 'cut- ;ofi' :relay' CO; The cutoff, relayconnects the line Let its front contacts .to the tap and ring "terminalsof the jack .l and at the same time disconnects the line L fro nftheline relay LR, the steppin ,,,,relay sue-d the progranr connections 11lead ng to the switch DH. The call is then completed in the usualmanner. At the end of the conversation the subscriber hangs up hisreceiver and the operator withdraws the plug from the jack J, releasingthe cut-off relay CO. This at once connects the line L to the progren'aconnections 11 and the subscriber may continue to hear the program beingtransmitted.

If. while the. program is being received, a telephone call should comein for line L, the operator will. insert. the plug of her cord into thejack J, thereby operating the cut-ofl' relay as before. The line L willnow be disconnected from the program connections and will be connectedover the front contacts of the cut-off relay to the terminals of thejack J. In 'onswer' to the ringing signal, the subscriberwill remove hisreceiver i-rom the switchhook and disconnect the loud speaker LS. Itwill be observed that it the line is beingused for telephonic purposesit is impossible to set the directive switch DR, for the key K isdisconnected as soon'ns the subscriber removes 'his receiver from theswitchhook and the selecting relay SR at the central station isdisconnected as soon as the cut-ofi' relay CO is operated.

The same arrangements may be used for selecting any one of u number ofcarrier programs as illustrated in Fig. 2. In this case. where theprograms are transmitted at carrier frequenciesit is to be observedthntthe line may be used simultaneously for receiving programtransmission und'for ordinary telephonic. purposes. Consequently, theconnections ,11 extending to the wipers 12 of the directive switch nreextended .to

the tip and ring sides of the line L adjacent lzothe armatureconnections of the cut-off relay, so that the operation of the cut oifrelay will not disconnect the rogram connectionsll from the line L, t ecut-off relay in this instance merely serving to disconnect the linerelay LR and the stepping relay SR.

' At the subscribers station the loud spealc er LS is bridged across theline independently oi? the switchhook 10, so that the re- .niovnlofzth'e mceiver from the switclihooli .cloes not disconnect the loudspeaker.

by the use of the directive selective switch,

it is possible to useithe sumecnrrier frequency for all of the programs$11106 but one program will be transmitted over a line at a time. At thesubscribers station it will be'necessaryto provide suitable detect ingapparatus and in most cases amplifying apparatus, as conventionallyindicated at AD, in order toitranslate the carrier program into voicefrequency currents for operating the loud speaker. No selectingupparatus is necessary at the subscribers station even in the case ofcarrier transmission, except a single high pass filter conventionallyindicated at HP, this filter being provided to prevent the voicefrequency currents transmitted O'\1.",tl1e line from actuating the loudspeaker. The high pass filter will, of course, pass the carrierfrequencies used for program transmission, regardless rent step ingrelay SR. Itwill be observed that if t e subscriber removes hisreceiverfrom the switchhook, he will be able to hear the current from the sourceG, as said source is, in effect, bridged across the two sides of theline through the windings of the relay SR and over the back contacts ofthe cut-ofi' relay C0. As soon as the operator answers his signal,however, the cut-off relay CO is operated and in connecting theterminals of the line to the jack J, the cutoti' relay functions todisconnect the relay SR as well as the line relay LR from the line,Consequently, the tone due to the al- .ternnting current source willcease before any conversation takes place over the line. The operationof the circuit of Fig. 3 is otherwise similar to that of Fig. 2 and neednot be further described.

It will be obvious that the general principles herein disclosed may beembodied in many other organizationswidely different from thoseillustrated without departing from the spirit of the invention asdefined in the appended claims.

What is claimed is:

1. In a program distribution system, a. subscribefis telephone lineterminating in a subscrihers telephone apparatus at the subscribersstation, switching means at the cen-.

trnl office whereby connect-ions may be established between saidsubscribers line and another subscribers line, a plurality of trunks atthe cent-rel oilioe upon which programs may .be impressed, atdirectively operuted.

switch independentotsaid first mentioned switching means at the centraloilice for-establi'shing connections between said first mentioned lineand any desiredtru'nk to the exclusion of other trunks, an alternatingcurrent control device for operating said switch, and means to controlthe transmission of alternating current to said device from thesubscribefs station over the two sides of said first mentioned line inseries.

2. In a program distribution system, a

snhscrihers telephone line terminating in a subscribefis telephoneapparatus at the subscribers stat-ion, switching means at the cen traloffice whereby connections may be est-ablished between said subscribersline and onother subscribers line, a plura'lity ot' trunks at thecentral oflice upon which programs may be impressed, an impulse-operatedswitch independent of said first mentioned switching met-111s at thecentral office to select any trunk to the exclusion of the others, analternating current responsive device for controlling the operation ofsaid'swit'ch, and means at the subscribers station for controlling thetransmission of impulsesot' alternating current "over the two sides ofsaid first mentioned line in series to operatesaid device.

3. In a program distributionsystem, a subscribers telephone lineterminatingin' a subscribers telephone apparatus at the subscribersstation, switching means at the central oflice whereby connect-ions maybe established between said subscribers line and another subscribersline, a plurality of trunks at. the central oflice upon which programsmay be impressed, an impulse-oper ated selecting switch independent ofsaid first mentioned switching means at the 'centrill oflice to selectany trunk to the exclusion of the others, an alternating currentresponsive device for controlling said switch, an impulse sender at thesubscribers stat-ion, and means whereby said sender may control thetransmission of impulses of alternating current over the two sides ofsaid first mentioned line in series-to operate said device.

4. In a program distribution system, an ordinary telephone subscribersline terminating in a subscribers telephone apparatus at the subscribersstation, switching meansat the central oifice for establishing connections between said. subscribers lineand other subscribers lines so thattelephone conversations may take place at ordinary telephonic"frequencies, a plurality of trunks at the cen tral ofiice upon whichdifferent programs may be impressed at carrier frequencies, adirectively operated switch independent-v of said first mentionedswitching means at the central 'oflice for establishing connectionsbetween said first'mentioned line and any desired trunk to the exclusionof other trunks,

controlling said switch, and means at the snb scribers station tocontrolthe trnnsniis- Si0l1 of alternating current over the two sides of saidfirst mentioned line in series to operate said device.

7 5. In a. program distribution system, 21 n ordinary telephonesnhscribers line. termi- Hating inn subscl'ihers telephone :ippnrntnsatthe .suhscnihefis station; switching means ant-the centre-l oflice'forestablishing connections between said snbserihers line and othersubscribers lines so that conversations may take plat-e atordinary,telephonic frequencies, a plurnlit of trunks n-t'the centrnloffice-upon which differentprograms may be impressed at carrierfrequencies, a step-W step switch indepemlontof said first.i,-ic'nitioned switching means at the central elite-e to select anytrunk .to the exclusion of the others, an nltei-nnting currentresponsive do Nicefor the. control. of said switch, nind means at theenlisciihers station tor-controlling the transmission of alternating;current over the ,two sides of said iii-st mentltm f-til line in seriesto operate saiddevice.

6. In a program distribution system, an ordinary telephone subscribersline terminating in n snbscrihere telephone z 'ipnrntns nt thesnhscribefs station, switching means at the central oll ice foresthhlishing connections between said snbscrihers line and othersnbrcrihei-S lines to thatconversations may take place at ordinnrytelephonicfrequencies, a plurality of trunks .nt thecentral oflice uponwhich. different programs n'layhe impressed nt, carrier freq uencit s,an impulseopei'ntcd switch independent of said first mentioned switchingmeans at the central oilice to select any trunk to the exclusion of theothers, an alternating current respon- MAURICE 1+3. STRIEBY.

